An aircraft is propelled by a number of turbojet engines each housed in a nacelle that also houses a collection of ancillary actuating devices associated with the operation thereof and performing various functions when the turbojet engine is operating or stationary. These ancillary actuating devices notably comprise a mechanical system for the actuation of thrust reversers.
A nacelle generally has a tubular structure comprising an air intake forward of the turbojet engine, a middle section intended to surround a fan of the turbojet engine, a rear section that may house thrust reversal means and intended to surround the combustion chamber of the turbojet engine, and generally ends in a jet pipe, the outlet of which is situated downstream of the turbojet engine.
Modern nacelles are often intended to house a bypass turbojet engine capable, via the blades of the rotating fan, of generating a flow of hot air (also known as the primary flow) from the turbojet engine combustion chamber.
A nacelle generally has an outer structure, known as the Outer Fixed Structure (OFS), which, together with a concentric inner structure, known as the Inner Fixed Structure (IFS), defines an annular duct for flow, also known as a flow path, intended to channel a flow of cold air, known as the secondary flow, which passes around the outside of the turbojet engine. The primary and secondary flows are ejected from the turbojet engine via the rear of the nacelle.
Each airplane propulsion unit is thus formed of a nacelle and of a turbojet engine, and is suspended from a fixed structure of the airplane, for example under a wing or on the fuselage, via a pylon or a strut attached to the turbojet engine or to the nacelle.
The rear section of the outer structure of the nacelle is usually formed of a first and of a second half-shell of substantially semicylindrical shape, one on each side of a longitudinal vertical plane of symmetry of the nacelle, and movably mounted such that they can be deployed between a working position and a maintenance position with a view to providing access to the turbojet engine. The two half-shells are generally pivot-mounted about a longitudinal axis that forms a hinge in the top part (in the 12 o'clock position) of the reverser. The half-shells are kept in the closed position by means of locking devices positioned at least along a meeting line situated in the bottom part (in the 6 o'clock position).
Conventionally, the nacelle is equipped with at least one locking system designed to lock one of the half-shells relative to the other, it being possible for the locking system to be actuated between a locked state and an unlocked state using an actuating device.
The actuating device is generally in the form of a handle connected to a first end of a control rod mounted such that it can be moved translationally relative to the corresponding half-shell, the second end of the rod being connected to the actuating system.
The translational movement of the handle by an operator unlocks or locks the locking system.
A nacelle such as this has the disadvantages listed hereinbelow.
In order to ensure that the locking system is correctly locked or correctly unlocked, the handle has to be moved over the full length of its travel.
There is therefore a risk that an operator will move the handle translationally over just part of the handle travel, with the result that the locking system will not be correctly actuated.
This may have repercussions during flight, when the locking system is not correctly locked. Furthermore, if the locking system is incompletely unlocked, there is a risk that the nacelle will become damaged during maintenance operations when the two half-shells are parted from one another.
Another known actuating device comprises a rod that can move only in terms of rotation. This type of actuating device generally entails a preloading on the part of the operator, in order to actuate the locking system. When such a device is applied to a locking system that does not require preloading, the operator may consider the nacelle to have a locking fault and that additional checks need to be performed as a result.